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National Geologic Map Database

Geologic Unit: Empire

Usage:

Empire Formation of Ravalli Group of Belt Supergroup (MT*)


Geologic age:

Middle Proterozoic*


Type section, locality, area and/or origin of name:

Type localities are on ridge north of Empire [2 mi west of Marysville] and in canyon walls just below Marysville, Lewis and Clark Co., west-central MT. Named from exposure west of Empire Mine, at head of Lost Horse Gulch in western part of Marysville district, Lewis and Clark Co., west-central MT (Walcott, 1899; see also Knopf, 1950).
Formation was found to be best exposed in section that extends east-west through USGS benchmark 4450 in Scratchgravel Hills, northwest of Helena (see Knopf, 1950).


AAPG geologic province:

Northern Rocky Mountain region*


For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.

Asterisk (*) indicates published by U.S. Geological Survey authors.

"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).

Slash (/) indicates name does not conform with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005). This may be explained within brackets ([ ]).